Sunday, March 30, 2014

We
are looking for a highly motivated recent graduate (BS, BA) to help kick-start the
new lab of Prof. Tobias Overath (http://people.duke.edu/~jto10)
at the Duke Institute for Brain Sciences (DIBS). Work in the lab investigates
how sounds, from simple sinusoids to complex speech signals, are processed in
the human brain, while tracking the underlying neural processes using a combination
of behavioral (psychoacoustics) and neuroimaging methods (fMRI, EEG).

An
ideal candidate will have received an undergraduate degree in psychology,
neuroscience, biomedical engineering, or a related field, by summer 2014, and will
have some familiarity with fMRI, EEG, and/or other experimental techniques. An
interest in how the brain processes sound is a strong plus, as is excellent knowledge
of at least one programming language (preferably Matlab). We are looking for a
lab manager who is conscientious and dependable as well as highly
self-motivated and pro-active.

The
main duties of the lab manager position will focus on (1) initially getting the
new lab up and running (e.g. ordering of equipment), (2) organizational tasks
(e.g. logistics, IRB, subject recruitment, teaching materials), and (3)
scientific tasks (e.g. design, implementation, analysis and write-up of
experiments). The balance of these tasks will shift gradually towards (3), and
the lab manager will have the chance to learn many skills that will be relevant
to pursuing a career in science or medicine.

The
position is available for an initial one-year period starting this Fall 2014,
with the potential for renewal. Salary will be $31,000 p.a. plus benefits.

To initiate
an application for the position, please email the PI Tobias Overath (t.overath@duke.edu)
by April 15, 2014 (later applications will also be considered if the position
is not filled), including the following documents: (1) a brief statement about
yourself and why you are interested in the position, (2) a resume that includes
brief descriptions of past research experiences, programming knowledge,
relevant courses and grades, and (3) the names and email addresses of 2
references who could be contacted (at least one reference should be able to
speak to your research background).

A recent paper in Nature
and a recent paper in Science provide
ECog evidence for dorsal stream function and STG function, respectively.

The first paper, “Sensory–motor transformations for
speech occur bilaterally,” is from my NYU colleague Bijan Pesaran’s lab;
the first author is Greg Cogan, a post-doc with Bijan. The paper tackles the
important question of how dorsal stream structures implement sensory–motor transformations, an issue that
Greg Hickok and I have speculated about (and Greg H. has worked on
extensively). This rich paper reports a bunch of cool findings worth reading
and studying. One of the strong claims – the part of the data providing the
title – concerns the bilateral nature of (those parts of) the dorsal stream
underpinning sensory-motor transformations for speech. Previous work has argued
that output-related dorsal-stream processing is lateralized, certainly much
more strongly than ventral stream areas/functions. I still find that position
on the right track (cf. Hickok & Poeppel 2007), and I derive some special
frisson from the fact that Greg Cogan, the co-architect of this counter-argument,
was my graduate student and is an important collaborator. The data are the data
– so it’s now important to figure out the why/how/what/when of these two dorsal
streams. I am no apologist for lateralization in speech, but these data
certainly present a new interpretive challenge. Speculations, ideas, data
welcome.

The second paper, “Phonetic Feature Encoding in Human
Superior Temporal Gyrus,” is from Eddie Chang’s lab at UCSF and is
spearheaded by Nima Mesgarani (now faculty at Columbia University in the EE
department). Over the years, the evidence has steadily accumulated that STG is
the ‘home’ of acoustic-phonetic perceptual analysis. Previous ECog data,
including stimulation data, for example by Dana Boatman, Nathan Crone, and
colleagues, has been strong evidence for STG (e.g. for review, Boatman 2004, http://www.ncbi.nlm.nih.gov/pubmed/15037126).
This new work builds on those findings and demonstrates the sensitivity and
selectivity of this region. From data acquired while the patients listened to
spoken sentences (of numerous speakers), Nima et al. extracted activity
profiles of the electrodes to all English phonemes. Phonetic features turn out
to be an effective grouping principle (manner is especially prominent). Nima
had done a similar project in Shihab Shamma’s lab in his dissertation work (I
harassed him about it at his defense …) - but ferrets neither speak nor listen
to all that much human speech … In this new work, the acoustic-phonetic
encoding is elegantly described, providing some ways to think about the
intermediate representations that could link input-related spectro-temporal
processing to linguistic structures.

Friday, March 21, 2014

Dr. Deryk Beal, principal investigator and founder of the Speech Neurogenetics Laboratory at the University of Alberta, invites applications for a WCHRI (http://wchri.srv.ualberta.ca/) funded position in the areas of developmental cognitive neuroscience, speech motor control and their related underlying genetic contributions.Dr. Beal is interested in advancing our understanding of the genetic and neural contributions to speech motor control in typically developing children and adults as well as children and adults with developmental stuttering and other motor speech disorders. My laboratory is equipped with state-of-the-art data acquisition systems, analysis software, and full access to the Peter S. Allen MR Research Centre.Dr. Beal was awarded an innovation grant from the Women and Children’s Health Research Institute to support a PhD student or Postdoctoral Fellow. The Speech Neurogenetics Laboratory provides a rich and multidimensional advanced graduate or post-graduate training program as it is positioned within the Centre for Neuroscience, Institute for Stuttering Treatment and Research and Faculty of Rehabilitation Medicine. Collaborators on current projects span the University of Alberta, Boston University and the Nationwide Children’s Hospital at the University of Ohio.The candidate will be expected to oversee genetic family aggregation, neuroimaging and behavioural motor control experiments as well as to analyze behavioural and functional and structural MRI and DTI data, prepare manuscripts for publications and participate in conferences. There are many very strong opportunities for meritorious-based authorship.The successful applicant will have a master’s or doctoral degree in a field related to cognitive neuroscience, neuroscience, psychology, developmental psychology, medicine or speech pathology. Individuals with a background in electrical engineering, biomedical engineering or computer science also will be considered. The candidate should be able to work efficiently, independently and diligently. The candidate should also possess excellent interpersonal, oral and written communication skills and enjoy working as part of a diverse and energetic interdisciplinary team. Applicants are expected to have a strong research background in the design and statistical analysis of brain-imaging experiments and/or motor control and learning experiments. Programming skills (MATLAB, C++; Python) and experience with at least one of the neuroimaging analyses programs (SPM, FSL, Freesurfer, ExploreDTI) are strongly desirable.Approximate start date is Spring/Summer 2014. Successful candidates will participate fully in the activities of the laboratory including regular supervisory meetings, laboratory meetings and journal clubs.For consideration please send a statement of interest, a CV and a list of three potential referees via email to Deryk Beal, PhD (dbeal@ualberta.ca). The search will continue until the position is filled.Websites: http://www.ualberta.ca/~acn/Beal.htmlANDhttp://www.istar.ualberta.ca/ISTAR%20Staff/DerykBeal.aspx

Wednesday, March 5, 2014

As detailed in a 2012 Talking Brains post, Greg and colleagues have proposed a model for speech production that aims to synthesize research from motor control, psycholinguistics, and neuroscience. This year, the inaugural issue of Language, Cognition, and Neuroscience (a re-christening of Language and Cognitive Processes) was guest edited by Albert Costa and F. Xavier Alario. It featured an article by Greg outlining a descendent of this model, the Hierarchical State Feedback Control model (HSFC). This target article was accompanied by a number of commentaries, including one by co-authored by the two of us and Brenda Rapp, as well as a response by Greg.

We (Matt and Adam) wanted to take advantage of the extra space afforded by Talking Brains to continue this conversation. The H in HSFC emphasizes the key role of hierarchical representations in Greg's proposal. In this post, we'd like to articulate why psycholinguists and neuroscientists have argued that in addition to such hierarchical representations, distributed/parallel encoding plays a critical role in language production.

To orient the discussion, consider two classical types of neurocognitive representational structures from vision:

1) Hierarchical representations. In representations that have this type of structure, there is a mapping (a necessary relationship) between two sets of representations. Consider classic simple vs. complex cells (Hubel & Wiesel, 1962). Under this proposal, simple cells preferentially respond to oriented bars in particular locations in the visual field. By integrating responses over many simple cells, complex cells respond to oriented bars across multiple locations. Critically, there is a precise mapping between these two levels of representation; the response properties of complex cells are defined by a function stated over the response properties of simple cells.

2) Parallel, independent representations. In representations that have this type of structure, the relationship between the two sets of representations is not defined by a direct mapping which spells out one level in terms of the other; rather, they are independent dimensions of structure. These dimensions can be linked or bound together, but they need not necessarily co-occur. Consider Treisman and colleagues' classic Feature-Integration Theory, which claims that some dimensions of visual stimuli are initially processed independently and only later bound together. This proposal provides a ready account of illusory conjunctions (Treisman & Schmidt, 1982). For example, if letter identity and color are coded independently, this can explain how a display with green Xs and brown Ts can give rise to the erroneous perception of a green T; this percept would be unlikely if letter identity and color were encoded in a single representation. Critically, the two types of information must be encoded independently (but in parallel) for these illusory conjunctions to occur during the later process of binding.

The HSFC model emphasizes the role of hierarchical representations. There is abundant evidence that these play a role in speech production. With respect to speech motor control, many accounts adopt a syllable-sized, relatively coarse-grained specification of motor movements, which directly maps onto detailed information regarding the precise temporal and kinematic coordination involved in production. There is also evidence that there are multiple levels of segment-sized representations that specify different types of information. A classic distinction is between context-independent vs. position-specific aspects of sound structure. The context-independent representations encode information about the sounds (e.g., /t/ in table and stable), and these map to position-specific representations that spell out the details (e.g., table contains aspirated [th] and stable contains unaspirated [t]). Evidence that these constitute distinct levels of representation includes data from individuals with acquired speech impairment (Buchwald & Miozzo, 2011). While this is not directly specified in the current HSFC model, it is clearly consistent with the overarching account as noted in Greg's response.

But what we'd like to emphasize is that parallel, independent representations also play a key role in language production. In particular, there's abundant reasons to believe that at certain levels of representation syllabic and segmental structure are not organized in a strict hierarchical fashion, but rather form parallel aspects of form representation. A number of results suggest that rather than syllables being defined as chunks of segments, syllable structure defines a frame; segments are then bound or linked to positions within this frame (see Goldrick, in press, for review and discussion of other dimensions of phonological structure).

To make this contrast explicit, consider the syllable "cat." Under a strictly hierarchical theory, this syllable could be defined by a mapping from [kaet] to the component segment [k-Onset] [ae-Nucleus] [t-Coda]. Under a theory utilizing independent representations, there is a [Onset]-[Nucleus]-[Coda] syllable frame and, independently, three segments /k/, /ae/, /t/. The syllable is represented by the binding /k/-[Onset]; /ae/-[Nucleus]; /t/-[Coda].

The first form of evidence in favor of the independent representations perspectives comes from illusory conjunctions in production. Speech errors can result in the mis-ordering of segments. In the majority of these errors, the segments occur in the wrong syllable but the correct syllable position (e.g., bad cat misproduced as "bad bat"). However, a substantial minority (more than 20% of errors in corpora of spontaneous speech; Vousden, Brown, & Harley, 2000) result in error being produced in incorrect syllable positions (e.g., film misproduced as "flim"). Just as letter identity and color form independent, dissociable dimensions of visual representation, segment identity and syllable positions form dissociable dimensions of phonological representations in production.

Evidence from priming points to a similar conclusion. Colored object naming is facilitated by segmental overlap between the color and object name, even when the segments occur in different syllable positions (e.g., green flag; Damian & Dumay, 2009). In addition, production of phrases made up of two nonsense words is facilitated when the two nonsense words have syllables with the same structure compared to nonwords that do not have matching structures -- even when there are no segments shared across the two syllables (Sevald, Dell, & Cole, 1995). For example, repeating two nonwords that both start with CVC syllables (e.g., KEM TIL.FER) or CVCC syllables (KEMP TILF.NER) is faster than repeating nonwords that start with syllables with contrasting consonant-vowel patterns (e.g., KEM TILF.NER or KEMP TIL.FLER). This occurs in spite of the syllables sharing no segments (e.g., KEM and TIL).

Based on data such as these, psycholinguistic theories (e.g., Shattuck-Hufnagel, 1992) have proposed that syllables and segments are not related in a strictly hierarchical fashion, but rather form independent-yet-linked dimensions of sound structure. That's not to say that the links are purely arbitrary; only certain segments can be associated to particular syllable positions (e.g., in English, /ng/ can be associated to coda but not onset). But segments are not merely the "elaborated" form of syllabic chunks; they form independent entities.

While hierarchical representations are a critical part of speech production, it's important to acknowledge the critical role of non-hierarchical representation. Mirroring other domains of processing, both representational schemas serve critical functions in the neurocognitive mechanisms supporting speech.

Monday, March 3, 2014

A Post-Doc and a fullt-me research assistant position are available in the Communication Neuroimaging and Neuroscience Laboratory (CoNi Lab) at Arizona State University, directed by Dr. Corianne Rogalsky. Our research is devoted to the cognitive neuroscience of language and music in the healthy and damaged brain, using techniques including fMRI, DTI, neuropsychological testing, and high-resolution lesion mapping.

Post-Doc: Responsibilities will include designing and implementing fMRI and structural imaging studies aimed at understanding the neural computations contributing to speech comprehension in everyday communication, particularly focusing on the contributions of meta-linguistic processes such as working memory, cognitive control, and attention, broadly defined. All scanning is conducted at the Barrow Neurological Institute in downtown Phoenix, and there is access to stroke and aphasic populations through the ASU Speech & Hearing Clinic and numerous stroke facilities throughout the Phoenix area. Requirements include spoken and written proficiency in English, a Ph.D. in neuroscience, psychology, computer science, or a related field. Preference will be given to applicants who have evidence of successfully conducting fMRI experiments in the realm of cognition. Proficiency with the linux computing environment, E-prime, Matlab, AFNI, and/or FSL is preferred.

Research Assistant: Responsibilities will include behavioral and fMRI data collection, programming of experiments, contacting and scheduling research participants, and data scoring and analysis. These tasks require an applicant to have a strong initiative to problem solve, be self-sufficient, and efficiently multitask. Requirements include spoken and written proficiency in English, a minimum of a bachelor-level degree (e.g., BA or BS), preferably in psychology, neuroscience, computer science, or a related field, and willingness to make a 2-year commitment. Strong interpersonal skills and an ability to effectively recruit and work with participants (including special populations), and other members of the lab are essential. Preference will be given to applicants who also are proficient with the linux computing environment, are familiar with E-prime and/or Matlab, and/or have experience with neuroimaging analysis software such as AFNI or FSL.

The CoNi Lab is situated in the Department of Speech and Hearing Science at ASU. ASU is located in Tempe, Arizona, in the metropolitan Phoenix area, which has a thriving neuroscience and neuroimaging community including the Mayo Clinic and Barrow Neurological Institute. Tempe features 330 days of sunshine a year.

Applications will be reviewed as they are received. The preferred start date for both positions is July 1st, but slightly later start dates will also be considered. Both positions are funded for two years, with possible extensions pending funding. If interested, please email a brief cover letter (including a description of research interests, qualifications, future goals, and available start date), CV, reprints or preprints (for post-doc position), and contact information for two references to corianne.rogalsky@asu.edu. Arizona State University is an equal opportunity employer. Please visit neuroimaging.lab.asu.edu for more information about the CoNi lab.

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Greg Hickok is Professor of Cognitive Sciences at UC Irvine, Editor-in-Chief of Psychonomic Bulletin & Review, and author of The Myth of Mirror Neurons. DavidPoeppel, after several years as Professor of Linguistics and Biology at the University of Maryland, College Park, is now Professor of Psychology at NYU. Hickok and Poeppel first crossed paths in 1991 at MIT in the McDonnell-Pew Center for Cognitive Neuroscience where Hickok was a post doc, and Poeppel a grad student. Meeting up again a few years later at a Cognitive Neuroscience Society Meeting in San Francisco, they began a collaboration aimed at developing an integrated model of the functional anatomy of language. Research in both the Hickok and Poeppel labs is supported by NIDCD.